A battery cell includes a case that accommodates an electrode assembly and electrolytic solution. The electrode assembly has positive electrodes, negative electrodes, and separators that insulate the positive electrodes and negative electrodes from each other. The electrode assembly has a laminated structure in which each separator is arranged between a positive electrode and the corresponding negative electrode.
A battery module has battery cells arranged side by side. The battery cells are arranged in a direction in which the positive electrodes, the negative electrodes, and the separators are stacked in the electrode assembly, that is, in the lamination direction. The battery module also has two end plates that sandwich the battery cells from the opposite sides in the arrangement direction of the battery cells. Further, as disclosed in, for example, Patent Document 1, a cover is placed on the surfaces of the battery cells on which terminals are located in some cases to prevent adhesion of liquid and dust to the battery cells, and insulate and protect bus bar connecting portions between the terminals of the battery cells.
The battery cells expand through repetitive use. Specifically, repetitive charging and discharging of the battery cells causes the electrode assemblies inside the cases to expand in the lamination direction of the electrode assembly. With the expansion of the electrode assembly in the lamination direction, the side walls located in the lamination direction of the electrode assembly in the case are pushed, which deforms the case. Such expansion of the battery cell may apply load on the two end plates. In this regard, some battery modules are provided with an elastic body held between one of the end plates and a battery cell. According to this configuration, when the battery cells expand through repetitive use, the elastic body is elastically deformed to limit the load applied to the two end plates.
Connecting members of the battery cells are fixed to the cover in some cases. In this case, expansion of the battery cells moves the connecting members in the arrangement direction of the battery cells. However, if the cover cannot be moved in the arrangement direction of the battery cells, stress is applied to the connecting members between the battery cells and the cover, which may damage the connecting members. To cope with such a drawback, the battery module is provided with an attachment plate that is sandwiched between the elastic body and a battery cell and attached to the cover. With this configuration, expansion of the battery cells causes the connecting members, the cover, and the attachment plate to move integrally in the arrangement direction of the battery cells. This limits stress applied to the connecting members between the battery cells and the cover, so that the connecting members are restricted from being broken.